Plants growing in pots are much more vulnerable to frost than the same plants in the ground. In a border, the roots are insulated by the surrounding soil; in a container, they're only separated from freezing air by a thin wall of terracotta or plastic. A few cold nights can be enough to damage the roots of olive trees, bay trees, citrus, agapanthus and many tender shrubs.
The good news is that protecting container plants is quick, cheap and easy once you know what to do.
1. Know when to act
In most of the UK, the first frosts arrive between late October and mid-November, although sheltered city gardens may stay frost-free for longer. Keep an eye on the forecast and have your protection ready to go before temperatures are due to drop close to 0°C – it's much easier than rushing out on a cold evening.
2. Insulate the pot, not just the plant
It's the roots in the pot that are most at risk, so start there. Wrapping the container in an insulating layer keeps the root ball several degrees warmer on a frosty night. An insulated plant pot cover is the simplest option: it wraps around the pot, closes with a zip, and cinches around the trunk with a drawstring to keep cold air out. Unlike bubble wrap or hessian, it's quick to put on and take off, and you can fold it away and reuse it next winter.
3. Raise pots off the ground
Standing pots directly on a patio lets water sit underneath them, which can freeze and crack the pot or leave roots waterlogged. Lift containers onto pot feet, bricks or small wooden blocks so excess water can drain away freely.
4. Move pots somewhere sheltered
If you can, group pots together against a south- or west-facing house wall. The wall radiates warmth overnight and grouping the pots together means they shelter each other. Avoid frost pockets at the bottom of slopes, and keep tender plants out of cold, drying winds.
5. Water less, but don't let them dry out
Plants need much less water in winter, and soggy compost freezes more easily. Water sparingly on mild days, ideally in the morning, and only when the top few centimetres of compost feel dry.
6. Protect the top growth of tender plants
For plants such as tree ferns, bananas or young citrus, add a layer of horticultural fleece over the foliage on the coldest nights. Remove it on mild days so the plant can breathe and get light.
7. Don't forget in spring
Keep protection handy until the risk of frost has passed – in much of the UK that's around mid-May. Once the weather settles, remove covers, give pots a tidy and a feed, and your plants will be ready for another season.
Quick winter checklist for container plants
- Wrap pots in an insulating cover before the first frost
- Raise pots onto feet for drainage
- Group pots against a sheltered, warm wall
- Water sparingly, only when the compost is dry
- Use fleece over tender foliage on the coldest nights
Looking for more ways to get your garden ready for the colder months? Browse our Garden Storage & Covers and the rest of our Garden & Outdoor range.